1. Field of the Invention
This invention provides an improved cutter design for size reduction equipment as used in plastic or other waste material recovery systems. A first objective of the invention is to provide a cutter arrangement which provides predetermined, uniform granulate size for subsequent processing equipment. Other objectives will be shown in the following description.
Size reduction equipment has recently been developed for plastic and related industries which offers significant advantages over the prior art. An example of this size reduction equipment is Model BC-30 manufactured by Allegheny Recycling and Waste Reduction Equipment, Inc. of Delmont, Pa. (The aforementioned equipment is based on teh patents of Lodovico et al, U.S. Pat. Nos. 4,669,673, and 4,750,678, which have been assigned to John W. Wagner of the Allegheny Recycling company.) This equipment enhances reprocessing production by providing uniform granulate size among that portion of the granulate which has been properly formed. However, an inherent disadvantage of this equipment is the inadvertent production of a mix of properly formed granulate with improperly formed shreds.
The present invention is a further refinement within the secondary cutter area of this newer equipment which eliminates shred formation. The result is a granulate with a predetermined, uniform size.
2. Description of the Prior Art
For the purposes of definition as used in describing the end product of the plastic size reduction process, the term "granulate" will mean any finished product after final processing, irrespective of size. The term "fine" will mean a granulate which is substantially less in dimension than that which is desired. The term "shred" will indicate a finished material which is properly sized in one dimension when viewed in a two dimension plane, but is of excessive length in the other. And finally, the term "chip" will mean a two dimensioned granulate which is formed with a prescribed dimension in both its length and width.
It should be obvious to the trained observer that the processing horsepower requirements of this technology are in direct relationship to the size reduction of the granulate. That is, each cut of the individual granulate requires power input until said granulate is discharged from the screen area of the equipment. When size reduction takes place beyond optimum size requirements, such as when fines are produced, the horsepower requirements of the equipment are increased without a corresponding increase in material throughput or quality. In practice, it has been shown that the horsepower requirements for processing a given weight of material is considerably less when all size reduction to the material is accomplished during a single pass through any portion of the equipment, as against multiple passes through the same equipment when the granulate size is allowed to exhibit a random distribution of size.
Thus, it can unequivocally be stated that size reduction equipment which processes the granulate in a single pass greatly reduces the power requirements for the process. Consequently, the equipment supplied by Allegheny Recycling and Waste Reduction Equipment, Inc. achieves a greatly enhanced throughput rate for a given horsepower as compared with recirculating bed knife systems.
However, effective as the Allegheny system is in reducing the power requirements of the process, it has the shortcoming of producing properly sized chips in combination with shreds. This is an acceptable approach if size reduction of waste is the sole objective. (Though it must be pointed out that material reduced to chips will occupy considerably less volume than the same material reduced to shreds.) However, when reprocessing of the granulate is the objective (such as is the case in plastic recovery systems) the presence of shreds becomes a major obstacle.
Lodovico et al, in attempting to correct this shortcoming, has patented a system which uses both a primary and a secondary cutting section. This approach reduces the horsepower requirements for processing a given weight of waste material. Nonetheless, there are certain shortcomings in this system which this invention seeks to remedy.
This invention comprises an improvement in the Allegheny two-stage cutter design (which henceforth will be referred to as Lodovico et al.). The first stage of this present invention is the subject of a prior patent application entitled CUTTER ENHANCEMENT FOR PLASTIC SIZE REDUCTION EQUIPMENT, Ser. No. 07/595,258. The second stage of this invention is an improvement over the prior art found in the Lodovico two-stage design, as stated in the first claim of U.S. Pat. No. 4,669,673.
The technology of this invention differs from that of Lodovico et al. in the following ways:
1. A larger diameter secondary cutting rotor is used resulting in a better cutting action of the shred. PA1 2. An open secondary cutting rotor is used which allows better chip dispersal and reduces undesirable additional cutting action. PA1 3. Deflector plates are used which guide the material into the secondary cutting area. PA1 4. A feed roller system is used which controls the rate of shred cutting by the secondary cutting rotor. PA1 5. The center line of the secondary cutter is substantially located on an imaginary line between the outlet portion of the primary cutters and the bed knife. Further, the imaginary line is essentially the plane of discharge of the shredded material. PA1 6. A negative pressure material blower is advantageously added at the discharge area of the secondary cutting section resulting in better material feed through the primary and feed sections of the machine. Said material blower further reduces turbulence in the secondary cutting section reducing undesirable chip cutting. PA1 7. The primary cutting section is structurally separate from the feed section. This allows ready removal of the primary cutting section for maintenance. PA1 1. It is the general objective of this invention to provide a size reduction machine for waste material (most generally plastic) which will produce a uniform chip size with a single pass through said machine. PA1 2. Another objective of the invention is to provide a cutting action which reduces the required horsepower for a given quantity of through-put. PA1 3. Another objective of the invention is to provide a means of regulating the feed rate to the secondary cutting section which is both positive and yet simple. PA1 4. A final objective of the invention is to provide a complete unit which is both robust and simple, yet which allows ease of removal of the primary cutter assembly.
Thus, I am suggesting that the invention I am offering is both novel as compared with the prior art and will offer the end user significant utilitarian advantages.